Apparatus for, system for and methods of maintaining sensor accuracy

ABSTRACT

Methods of maintaining accuracy in the measurement of one or more parameters of industrial water in industrial water systems are provided. The methods include the use of physical and/or chemical procedures to prevent and/or remove deposition from one or more surfaces utilized in measurement of the one or more parameters. The deposition may be caused by, for example, corrosion, fouling, or microbiological growth.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.14/594,589, filed Jan. 12, 2015, and granted as U.S. Pat. No. 9,772,303on Sep. 26, 2017, the entire contents of which are incorporated byreference.

BACKGROUND

Many industrial water systems require precise chemical treatment for anyone or combination of the following: maintaining superior energytransfer, reducing waste, protecting assets, and improving productquality. Precise chemical treatment can be administered to an industrialwater system by monitoring characteristic variables such as, e.g.,conductivity, pH, oxidation-reduction potential, microorganismconcentration, alkalinity, and hardness.

Measured changes in any of these variables can provide input intocontrolling process operations. For example, a measured increase inconductivity of cooling water circulating in a cooling tower operationmay trigger a blow down of the operation followed by addition of make-upwater, thereby reducing the conductivity of the cooling water.Maintaining accurate, precise measurement of characteristic variables ofan industrial water system, particularly a cooling water system, is keyto its efficient treatment and operation.

For industrial water systems, more particularly cooling water systems,three issues are generally addressed by treatment operations: 1)Inhibition of scaling caused by mineral deposition, e.g., calciumcarbonate and/or magnesium silicate; 2) Inhibition of fouling caused bydeposition of suspended deposits caused by, e.g., corrosion; and 3)Inhibition of microbial contamination caused by, e.g., bacteria, algae,and/or fungi. Any of these conditions may cause deposits to form onwetted surfaces, particularly surfaces that are utilized in measurementof a parameter of the industrial water system. Deposition of any ofthese onto a measurement surface are of particular concern, asdeposition can introduce measurement error (inaccuracy, imprecision, orboth) caused by, e.g., delayed measurement response time, measurementdrift (e.g., changing offset), or measurement instability.

Several sensor probe cleaning devices and methods are available. Forexample, ultrasonic cleaning techniques exist for liquid systemscomprising dissolved gases. Mechanical wiping systems have beenimplemented in some applications. Air jet, water jet, and off-linechemical treatments have been used as well.

SUMMARY

Methods of maintaining accuracy in measuring a parameter of anindustrial water system are provided. In an aspect, the method comprisescontacting a liquid stream at a liquid stream pressure with a surfaceutilized for measuring a parameter with a sensor. A gaseous stream isintroduced into the liquid stream, thereby causing the combined gaseousand liquid stream to contact the surface. The gaseous stream isintroduced into the liquid stream at a gaseous pressure of from about 10psi to about 100 psi greater than the liquid stream pressure.

In a further aspect, the method comprises contacting an industrial waterstream at an industrial water stream pressure with at least one of awetted surface of a pH sensor and a wetted surface of anoxidation-reduction potential sensor. The pH and/or oxidation-reductionpotential of the industrial water stream is measured. A cleaningsolution comprising urea hydrogen chloride is contacted with at leastone of the wetted surfaces for a first period of time and at aconcentration sufficient to clean the at least one of the wettedsurfaces. The industrial water stream is re-contacted with the cleanedat least one of the wetted surfaces at the industrial water streampressure for a second period of time, thereby measuring pH and/oroxidation-reduction potential of the industrial water stream usingcleaned pH and/or oxidation-reduction potential sensors. A recoverycurve is created that is related to the measured pH and/or the measuredoxidation-reduction potential using the cleaned pH and/oroxidation-reduction potential sensors. The aforementioned steps arerepeated. The respective recovery curves are compared. If the comparisonof the respective recovery curves demonstrates acceptable sensordegradation, the respective sensor may remain in service. However, ifthe respective sensor demonstrates unacceptable sensor degradation, therespective sensor is removed from service.

In yet another aspect, the method comprises contacting an industrialwater stream at an industrial water stream pressure with at least one ofa wetted surface of a pH sensor and a wetted surface of anoxidation-reduction potential sensor. A cleaning solution is contactedwith at least one of the wetted surface of the pH sensor and the wettedsurface of the oxidation-reduction potential sensor. The industrialwater stream is re-contacted with at least one of the wetted surface ofthe pH sensor and the wetted surface of the oxidation-reductionpotential sensor at the industrial water stream pressure. A gaseousstream is introduced into the industrial water stream at a gaseousstream pressure of from about 10 psi to about 100 psi greater than theindustrial water stream pressure and after initiation of there-contacting.

A method of maintaining accuracy in the measurement of a plurality ofparameters of industrial water in an industrial water system is alsoprovided. The method comprises contacting an industrial water stream atan industrial water stream pressure with a plurality of surfacesutilized for measuring a plurality of parameters with a plurality ofsensors. A first subset of the surfaces is isolated from the industrialwater stream while a second subset of the surfaces maintains contactwith the industrial water stream. At least one surface of the firstsubset is cleaned while the second subset maintains contact with theindustrial water stream. Contact with the industrial water stream isrestored with the first subset of surfaces. The first subset of surfacescomprises at least one of a wetted surface of a light transferencemedium, a wetted surface of a pH sensor, and a wetted surface of anoxidation-reduction potential sensor. The second subset of surfacescomprises at least one of a wetted surface of a corrosion detectionsensor and a wetted surface of a conductivity sensor.

In a further aspect, an apparatus for maintaining accuracy in themeasurement of a parameter of industrial water is provided. Theapparatus comprises a body having a top portion, a bottom portion, anentry portion, and an exit portion. The apparatus includes at least onesensor aperture formed into the top portion and extending partiallythrough the body toward the bottom portion. The at least one sensoraperture is configured to accept at least one sensor for measuring theparameter of industrial water. The apparatus includes a liquid flow boreformed through the body between the entry portion and the exit portion.The liquid flow bore fluidly communicates with the at least one sensoraperture and configured to allow a liquid stream to flow through thebody. The apparatus includes a gas flow bore formed at least partiallythrough the body. The gas flow bore is configured to allow a gaseousstream to flow into the body. The apparatus also includes at least onejet channel formed in the body and fluidly connecting the gas flow boreand the liquid flow bore. The at least one jet channel terminates in theliquid flow bore substantially opposite the at least one sensor apertureso as to direct the gaseous stream from the gas flow bore into theliquid flow bore toward the at least one sensor aperture.

In yet another aspect, an industrial water measuring system is provided.The system comprises an apparatus configured to maintain accuracy in themeasurement of a parameter of industrial water. The apparatus comprisesa body having a top portion, a bottom portion, an entry portion, and anexit portion. The apparatus includes a liquid flow bore formed throughthe body between the entry portion and the exit portion. The liquid flowbore is configured to allow a liquid stream to flow through the body.The apparatus includes at least one sensor aperture formed into the topportion of the body and extending at least partially through the body tofluidly communicate with the liquid flow bore at a sensor opening of theat least one sensor aperture. The apparatus also includes a gas flowbore formed at least partially through the body. The gas flow bore isconfigured to allow a gaseous stream to flow into the body. Theapparatus includes at least one jet channel formed in the body andfluidly connecting the gas flow bore and the liquid flow bore. The atleast one jet channel terminates in the liquid flow bore substantiallyopposite the sensor opening of the at least one sensor aperture. Thesystem also includes at least one sensor disposed in the at least onesensor aperture. The at least one sensor includes a surface disposed inthe sensor opening so as to sense a parameter of the liquid streamflowing through the liquid flow bore. The at least one jet channel isconfigured to direct at least a portion of the gaseous stream from thegas flow bore into the liquid flow bore toward the surface of the sensordisposed in the sensor opening of the at least one sensor aperture so asto clean the surface of the sensor.

In another aspect, an apparatus for maintaining accuracy in themeasurement of a parameter of industrial water is provided. Theapparatus comprises a body having a top portion, a bottom portion, anentry portion, and an exit portion. The apparatus includes a liquid flowbore formed through the body between the entry portion and the exitportion. The liquid flow bore is configured to allow a liquid stream toflow through the body. The apparatus includes a first sensor apertureformed into the top portion substantially perpendicular to the liquidflow bore and extending partially through the body to fluidlycommunicate with the liquid flow bore at a first sensor opening. Thefirst sensor aperture is configured to accept a first sensor formeasuring the parameter of industrial water. The apparatus includes asecond sensor aperture formed into the top portion substantiallyperpendicular to the liquid flow bore and extending partially throughthe body to fluidly communicate with the liquid flow bore at a secondsensor opening. The second sensor aperture is configured to accept asecond sensor for measuring a parameter of industrial water. Theapparatus includes a gas flow bore formed at least partially through thebody substantially parallel to the liquid flow bore. The gas flow boreis configured to allow a gaseous stream to flow into the body. Theapparatus includes a first jet channel formed in the body substantiallyperpendicular to the liquid flow bore and fluidly connecting the gasflow bore and the liquid flow bore. The first jet channel terminates inthe liquid flow bore substantially opposite the first sensor opening ofthe first sensor aperture so as to direct at least a portion of thegaseous stream from the gas flow bore into the liquid flow bore towardthe first sensor opening. The apparatus includes a second jet channelformed in the body substantially perpendicular to the liquid flow boreand fluidly connecting the gas flow bore and the liquid flow bore. Thesecond jet channel terminating in the liquid flow bore substantiallyopposite the second sensor opening of the second sensor aperture so asto direct at least a portion of the gaseous stream from the gas flowbore into the liquid flow bore toward the second sensor opening.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

FIG. 1a illustrates a perspective view of an apparatus that may be usedto perform methods of the present disclosure;

FIG. 1b illustrates a sectional view of an apparatus that may be used toperform methods of the present disclosure;

FIG. 1c illustrates an embodiment of an optical sensor that may be usedto perform methods of the present disclosure;

FIG. 1d illustrates an embodiment of an apparatus that may be used toperform methods of the present disclosure;

FIG. 1e illustrates a plan view of an embodiment of a system that may beused for performing methods of the present disclosure;

FIG. 2 illustrates a plan view of an embodiment of a system that may beused for performing methods of the present disclosure;

FIG. 3 illustrates a plan view of an embodiment of a system that may beused for performing methods of the present disclosure;

FIG. 4 illustrates oxidation-reduction potential measurement utilizingtwo oxidation-reduction sensor probes after chemical cleaning andexposed to a single industrial water stream;

FIG. 5 illustrates pH measurement utilizing a pH sensor probe afterchemical cleaning and exposed to an industrial water stream;

FIG. 6 illustrates oxidation-reduction potential measurement utilizingtwo oxidation-reduction sensor probes after chemical cleaning andexposed to a single industrial water stream, wherein one of the twoprobes is further exposed to a gaseous stream post-chemical cleaning;

FIG. 7 illustrates a plan view of an embodiment of a system that may beused to perform methods of the present disclosure;

FIG. 8 is a plot of results related to Example 1 herein;

FIG. 9 is a plot of results related to Example 2 herein; and

FIG. 10 is a plot of results related to treatment with a mineralacid-based cleaning solution of Example 3 herein.

FIG. 11 is a plot of results related to treatment with a urea salt-basedcleaning solution of Example 3 herein.

DETAILED DESCRIPTION

While embodiments encompassing the general inventive concepts may takevarious forms, there is shown in the drawings and will hereinafter bedescribed various illustrative and preferred embodiments with theunderstanding that the present disclosure is to be considered anexemplification and is not intended to be limited to the specificembodiments.

Generally, methods of maintaining accuracy in the measurement of aparameter of industrial water, which may be cooling water, are provided.“Cooling water” refers to a liquid substance comprising water that iscirculated through a system of one or more conduits and heat exchangeequipment thereby transferring heat energy from one substance toanother. The substance that loses heat is said to be cooled, and the onethat receives heat is referred to as the coolant.

A general goal of conducting the methods disclosed herein is to maintainaccuracy in measurements performed in monitoring and optionallycontrolling industrial water systems by way of preventing depositiononto a surface critical to performing said measurements. Another generalgoal of conducting the methods disclosed herein is to remove depositionfrom surfaces critical to performing said measurements, therebyrestoring accuracy that may have been lost because of the deposition.The deposition may be due to scaling, fouling, microbiological growth,or combinations thereof.

A more specific goal of conducting the methods disclosed herein is toprevent deposition onto at least one of a wetted surface of a pH sensor,a wetted surface of an oxidation-reduction potential sensor, and awetted surface of a light transference medium used in an industrialwater system, thereby maintaining an acceptable level of accuracy inmeasurements made from the utilized sensor(s). Another more specificgoal of conducting the methods disclosed herein is to remove depositiononto at least one of a wetted surface of a pH sensor, a wetted surfaceof an oxidation-reduction potential sensor, and a wetted surface of alight transference medium used in an industrial water system, therebyrestoring a level of accuracy that may have been lost because of thedeposition.

As it pertains to this disclosure, unless otherwise indicated,“industrial water” refers to a liquid or a mixed state substancecomprising a liquid, wherein the liquid comprises water, and wherein theliquid or mixed state substance is used for an industrial purpose. Byway of example, a non-exhaustive list of industrial purposes includesthe following: heating, cooling, manufacturing (e.g., papermaking),refining, chemical processing, crude oil extraction, natural gasextraction, and the like. “Cooling water” is an exemplary embodiment of“industrial water.”

As it pertains to this disclosure, unless otherwise indicated,“continuous(-ly)” describes performance of an action for an extendedperiod of time without interruption. An exemplary “extended period oftime” is 24 hours.

As it pertains to this disclosure, unless otherwise indicated, “pHsensor” refers to an electrode-type sensor utilized for measuring pH ofa liquid, which may or may not include a dedicated input device, adedicated output device, or a dedicated input-output device. Anexemplary embodiment of a pH sensor is Part No. 400-C0060.88, availablefrom Nalco, an Ecolab Company, 1601 West Diehl Road, Naperville, Ill.60563 (http://ecatalog.nalco.com/pH-Meters-Waterproof-C739.aspx).Certain pH sensors may measure parameters in addition to pH.

As it pertains to this disclosure, unless otherwise indicated,“oxidation-reduction potential sensor” refers to an electrode-typesensor utilized for measuring oxidation-reduction potential (“ORP”) of aliquid, which may or may not include a dedicated input device, adedicated output device, or a dedicated input-output device. Anexemplary embodiment of an oxidation-reduction potential sensor is PartNo. 400-P1342.88, available from Nalco, an Ecolab Company, 1601 WestDiehl Road, Naperville, Ill. 60563(http://ecatalog.nalco.com/ORP-Pocket-Meter-Waterproof-C732.aspx).Certain oxidation-reduction potential sensors may measure parameters inaddition to oxidation-reduction potential. Examples of other sensors,such as conductivity sensors and corrosion monitors, are also availablefrom Nalco, an Ecolab Company, 1601 West Diehl Road, Naperville, Ill.60563 (Nalco online Equipment Catalog can be found at the following url:http://ecatalog.nalco.com/Default.aspx).

As it pertains to this disclosure, unless otherwise indicated, a “periodof time” (e.g., a “first period of time”), when in reference tocontacting a cleaning solution to a wetted surface of a sensor (e.g., pHsensor, oxidation-reduction potential sensor, etc.), refers to, forexample, a period of time sufficient to remove at least a portion of, orsubstantially all, obstruction that may be found on the wetted surfaceof the sensor in contact with the cleaning solution, at a particularconcentration of cleaning solution. Exemplary ranges of periods of timefor contacting the wetted surface of the sensor with a cleaning solutioninclude, but are not limited to, from about 1 second, or from about 10seconds, or from about 30 seconds, or from about 1 minute, to about 2minutes, or to about 3 minutes, or to about 5 minutes, or to about 10minutes, or to about 30 minutes, or to about 1 hour, including fromabout 1 minute to about 5 minutes, and including from about 1 minute toabout 10 minutes, and including from about 1 minute to about 1 hour. Theperiod of time sufficient to clean a wetted surface using the methods ofthe present disclosure may vary depending on factors including, interalia, the chemical species of the cleaning solution, the concentrationof the cleaning solution, temperature, pressure, flow rate, turbulence,and the like.

As it pertains to this disclosure, unless otherwise indicated,“controller” refers to an electronic device having components such as aprocessor, memory device, digital storage medium, cathode ray tube,liquid crystal display, plasma display, touch screen, or other monitor,and/or other components. Controllers include, for example, aninteractive interface that guides a user, provides prompts to the user,or provides information to the user regarding any portion of the methodof the invention. Such information may include, for example, building ofcalibration models, data collection of one or more parameters,measurement location(s), management of resulting data sets, etc.

When utilized, the controller is preferably operable for integrationand/or communication with one or more application-specific integratedcircuits, programs, computer-executable instructions or algorithms, oneor more hard-wired devices, wireless devices, and/or one or moremechanical devices such as liquid handlers, hydraulic arms, servos, orother devices. Moreover, the controller is operable to integratefeedback, feed-forward, or predictive loop(s) resulting from, interalia, the parameters measured by practicing the method(s) of the presentdisclosure. Some or all of the controller system functions may be at acentral location, such as a network server, for communication over alocal area network, wide area network, wireless network, extranet, theInternet, microwave link, infrared link, and the like, and anycombinations of such links or other suitable links. In addition, othercomponents such as a signal conditioner or system monitor may beincluded to facilitate signal transmission and signal-processingalgorithms.

By way of example, the controller is operable to implement the method ofthe invention in a semi-automated or fully-automated fashion. In anotherembodiment, the controller is operable to implement the method in amanual or semi-manual fashion. Examples of the aforementioned variationsof the invention are provided herein in reference to the figures.

For example, a dataset collected from a liquid may include variables orsystem parameters such as oxidation-reduction potential, pH,concentrations of certain chemical species or ions (e.g., determinedempirically, automatically, fluorescently, electrochemically,colorimetrically, measured directly, calculated, etc.), temperature,turbidity, pressure, flow rate, dissolved or suspended solids, etc. Suchparameters are typically measured with any type of suitable datameasuring/sensing/capturing equipment, such as pH sensors, ionanalyzers, temperature sensors, pressure sensors, corrosion detectionsensors, and/or any other suitable device or method. Devices capable ofdetecting or sensing colorimetric, refractometric, spectrophotometric,luminometric, and/or fluorometric signals are of particular utility forthe present invention. Such data capturing equipment is preferably incommunication with the controller and, according to alternativeembodiments, may have advanced functions (including any part of controlalgorithms described herein) imparted by the controller.

Data transmission of any of the measured parameters or signals to auser, chemical pumps, alarms, or other system components is accomplishedusing any suitable device, such as a wired or wireless network, cable,digital subscriber line, internet, etc. Any suitable interfacestandard(s), such as an Ethernet interface, wireless interface (e.g.,IEEE 802.11a/b/g/n, 802.16, Bluetooth, optical, infrared, otherradiofrequency, any other suitable wireless data transmission method,and any combinations of the foregoing), universal serial bus, telephonenetwork, the like, and combinations of such interfaces/connections maybe used. As used herein, the term “network” encompasses all of thesedata transmission methods. Any of the components, devices, sensors,etc., herein described may be connected to one another and/or thecontroller using the above-described or other suitable interface orconnection. In an embodiment, information (collectively referring to allof the inputs or outputs generated by the method of the invention) isreceived from the system and archived. In another embodiment, suchinformation is processed according to a timetable or schedule. In afurther embodiment, such information is processed in real-time. Suchreal-time reception may also include, for example, “streaming data” overa computer network.

As it pertains to this disclosure, unless otherwise indicated, “controlscheme” refers to providing output from a controller based on input tothe controller as defined herein.

A method of maintaining accuracy in measuring a parameter of anindustrial water system is provided. The method comprises contacting aliquid stream at a liquid stream pressure with a surface utilized formeasuring a parameter with a sensor. A gaseous stream is introduced intothe liquid stream, thereby causing the combined gaseous and liquidstream to contact the surface. The gaseous stream is introduced into theliquid stream at a gaseous pressure of from about 10 psi to about 100psi greater than the liquid stream pressure.

FIGS. 1a and 1b illustrate an embodiment of an apparatus that may beused to carry out at least a portion of one or more of the inventivemethods described herein. In certain embodiments, apparatus 100 can beused as an industrial water measuring system for measuring and formaintaining accuracy of measurements of at least one parameter ofindustrial water used in an industrial water system. FIG. 1a shows aperspective view of apparatus 100, while FIG. 1b shows a more detailedsectional view of apparatus 100. As shown, apparatus 100 comprises body102 that is capable of supporting two sensors, pH sensor 110 a andoxidation-reduction potential sensor 110 b. However, a person ofordinary skill in the art will recognize that apparatus 100 can bedesigned and built to implement one, two, or any reasonable number ofsensors 110, that the positions of pH sensor 110 a andoxidation-reduction potential sensor 110 b can be swapped, or apparatus100 may implement two pH sensors 110 a or two oxidation-reductionpotential sensors 110 b. Additionally, it is contemplated that othersuitable types of sensors can be used. As shown in the figures, thesensors 110 a, 110 b can be supported within first sensor aperture 112 aand second sensor aperture 112 b formed in body 102.

Furthermore, FIG. 1c illustrates an embodiment of an optical sensor 110x, e.g., an embodiment of a fluorometer. In the embodiment of FIG. 1c ,optical sensor 110 x may be operably mounted in place of at least one ofpH sensor 110 a and oxidation-reduction potential sensor 110 b, using,e.g., apparatus 100. Optical sensor 110 x may utilize an optical windowor a reflective surface as its wetted surface 1110 x, as describedherein. As is the case with pH sensor 110 a and oxidation-reductionpotential sensor 110 b, a person of skill in the art will recognize thatapparatus 100 provides merely an embodiment of an apparatus that may beutilized to carry out the methods disclosed herein, or portions thereof,and that the present application should not be limited to apparatus 100.The term “optical window” is used to refer to a barrier that allows foroptical observation of a substance in a process. The optical observationmay be visually or electronically performed. Optical observation refersto any light-based form of observation. Examples of optical observationinclude, but are not limited to, fluorometry, absorption,spectrophotometry, imaging, and any combination thereof.

Referring again to FIG. 1a , body 102 of apparatus 100 includes frontportion 101, rear portion 103, entry portion 105, exit portion 107, topportion 109, and bottom portion 111. In some embodiments, fastenerchannels 113 are formed through body 102 between front portion 101 andrear portion 103 to accommodate fasteners, for example, bolts or screws.The first and second sensor apertures 112 a, 112 b are formed into topportion 109 of body 102. As shown in FIG. 1b , sensor apertures 112 a,112 b each include a bore portion 114 a, 114 b and a counterbore portion116 a, 116 b, though embodiments without a counterbore are contemplated.It is contemplated herein that the sizes of sensor apertures 112 a, 112b and associated parts can be sized to accept whatever sensor isdesirable for a given sensing application.

Referring to FIG. 1b , liquid flow bore 117 is formed through body 102substantially between entry portion 105 and exit portion 107. Althoughthe embodiment illustrated in FIG. 1b shows liquid flow bore 117 asbeing substantially perpendicular to the first and second sensorapertures 112 a, 112 b, other relationships between the bores arecontemplated. Liquid flow bore 117 comprises an ingress portion 119adjacent entry portion 105 of body 102, a narrowed portion 120, and anegress portion 121 adjacent the exit portion 107 of body 102. In someembodiments, ingress portion 119 and egress portion 121 can have largerdiameter than narrowed portion 122. Liquid stream 120 a enters ingressportion 119 of liquid flow bore 117 through ingress orifice 118 formedin entry portion 105. Once liquid stream 120 a has entered ingressportion 119, the liquid stream is optionally narrowed at aperture 121and flows through narrowed portion 122. Liquid stream 120 a then passesthrough an egress aperture 124, through egress portion 121 of liquidflow bore 117, and out of body 102 through an egress orifice 126 formedin exit portion 107. It is apparent that liquid stream 120 a, which inthe illustrated embodiment becomes the liquid stream flowing throughnarrowed portion 122 of liquid flow bore 117, may comprise industrialwater of an industrial water system, a cleaning liquid, a separatewater-containing liquid, or combinations thereof.

As shown in FIG. 1b , bore portions 114 a, 114 b of sensor apertures 112a, 112 b, fluidly communicate with narrowed portion 120 of liquid flowbore 117. First and second sensor openings 115 a, 115 b are formed atthe intersection between the respective first and second sensorapertures 112 a, 112 b and liquid flow bore 117. In certain embodiments,surfaces 1110 a, 1110 b of sensors 110 a, 110 b are disposed in sensoropenings 115 a, 115 b. As a result, liquid stream 120 a flowing throughbody 102 contacts pH sensor 110 a and oxidation-reduction potentialsensor 110 b at surfaces 1110 a and 1110 b thereof.

With continued reference to FIG. 1b , gas flow bore 128 is formed inbody 102 substantially parallel to liquid flow bore 117 to allow forflow of a gaseous stream 130 into the body for introduction into theliquid flow bore substantially opposite sensor apertures 112 a and 112b. Gas flow orifice 128 has a gas ingress portion 129 adjacent exitportion 107 and a narrowed gas portion 131. In the embodiment shown inFIG. 1b , first and second jet channels 132 a, 132 b are formed in body102 and provide fluid communication between the narrowed gas portion 131of the gas flow bore 128 and the liquid flow bore 117. The first jetchannel 132 a terminates in narrowed portion 122 of liquid flow bore 117at a first countersinked opening 2110 a, and second jet channel 132 bterminates in the narrowed portion of the liquid flow bore at a secondcountersinked opening 2110 b. The first countersinked opening 2110 aopens into narrowed portion 122 substantially opposite first sensoraperture 112 a, and second jet channel 132 b opens into the narrowedportion substantially opposite second sensor aperture 112 b. Althoughthe embodiment illustrated in FIG. 1b includes two jet channels 132 a,132 b corresponding to two sensor apertures 112 a, 112 b, it iscontemplated that different amounts of jet channels can branch from gasflow bore 128 depending on the number of sensors used in a givenapparatus, or the number of sensors that a user wishes to clean viaintroduction of a gaseous stream.

As shown in FIG. 1b , gaseous stream 130 is introduced into gas ingressportion 129 of gas flow bore 128 at a gas ingress orifice 133 formed inexit portion 107 of body 102. Gaseous stream 130 then passes through agas aperture 134 into narrowed gas portion 131 of gas flow bore 128.Gaseous stream 130 then splits into either the first or second jetchannels 132 a, 132 b and is expelled through the respective first orsecond countersinked openings 2110 a, 2110 b into narrowed portion 122of liquid stream 120, thereby creating a gaseous and liquid stream 150.For the embodiment illustrated in FIG. 1b , gaseous stream 130 isintroduced in a direction perpendicular to liquid stream 120, in thisinstance, narrowed portion 122. As illustrated, gaseous stream 130 isintroduced through two countersinked openings 2110 a and 2110 b,corresponding to each of the surfaces 1110 a and 1110 b of pH sensor 110a and oxidation-reduction potential sensor 110 b. Though optional,countersinked openings 2110 a and 2110 b of the embodiment illustratedin FIG. 1b are tapered to provide distribution across wetted surfaces1110 a and 1110 b of pH sensor 110 a and oxidation-reduction potentialsensor 110 b. In other embodiments, such as the embodiment shown in FIG.1d , jet channels 132 a, 132 b terminate into narrowed portion 122 atfirst and second nozzles 3110 a, 3110 b. In such embodiments, gaseousstream 130 enters narrowed portion 117 through nozzles 3110 a, 3110 bthat are not countersunk. As a result, gaseous stream 130 mixes with theliquid stream 120 as a more direct jet than when the countersinkedopenings 2110 a, 2110 b are used. In some embodiments, openings of firstand second nozzles 3110 a, 3110 b have a substantially smaller diameterthan the respective first and second jet channels 132 a, 132 b. As isevident from the embodiment illustrated in FIG. 1b , gaseous stream 130may be configured to operably supply a gaseous substance to a singlesurface, a plurality of gaseous substances to a plurality of surfaces, asingle gaseous substance to a plurality of surfaces, or however the usersees fit, using valves, conduits, fittings, and the like.

In certain embodiments, the liquid stream comprises, or may consist ofor consist essentially of, water. In a preferred embodiment, the liquidstream is an industrial water stream from an industrial water process.In other embodiments, the liquid stream may be a liquid cleaningchemical. In some embodiments, the surface is isolated as describedherein and the combined gaseous and liquid stream is contacted with thesurface. In some embodiments, the liquid stream contacts the surfaceduring isolation via circulation (e.g., recirculation), where the liquidstream may comprise industrial water from the industrial water process.

In certain embodiments, a liquid stream is contacted with a surfaceutilized for measuring a parameter with a sensor. The surface may beconnected to the sensor in the form of a wetted surface of the sensoritself, i.e., a sensing component of the sensor. The surface may be awetted surface of a light transference medium.

In certain embodiments, the liquid stream is contacted with a corrosioncoupon, which is removed and observed to evaluate for general and localcorrosion. When present, the corrosion coupon is exposed to the liquidstream generally following a standardized protocol, e.g., an ASTMstandard. The coupon can be removed from the liquid stream in order tomeasure e.g., weight loss or depth of pitting, when present.

In certain embodiments, the gaseous stream is introduced into the liquidstream, which may be an industrial water stream, at a gaseous pressureof from about 10 psi to about 100 psi greater than the liquid streampressure. The term “gaseous stream” refers to flow of a gas-phasesubstance. An exemplary embodiment of a gaseous stream is a stream ofcompressed air. The gaseous stream pressure may be at least about 10 psigreater than the liquid stream pressure, or about 20 psi greater thanthe liquid stream pressure, and up to about 100 psi greater than theliquid stream pressure, or up to about 80 psi greater than the liquidstream pressure, or up to about 60 psi greater than the liquid streampressure, or up to about 40 psi greater than the liquid stream pressure.In a preferred embodiment, the gaseous stream is introduced into theliquid stream at a gaseous pressure of from about 20 psi to about 40 psigreater than the liquid stream pressure.

In certain embodiments, the surface is located in a narrowed portion ofthe liquid stream, which may be an industrial water stream. In apreferred embodiment, the surface located in a narrowed portion of theliquid stream is at least one of a wetted surface of a pH sensor and awetted surface of an oxidation-reduction potential sensor. The flow ofthe liquid stream becomes narrowed just upstream from the surface, andthen a gaseous stream is introduced into the narrowed portion so as tocreate a combined gaseous and liquid stream, which thereby contacts thesurface. The narrowing of the liquid stream has been demonstrated toprovide particularly beneficial results when used in combination withthe introduction of the gaseous stream at a gaseous stream pressure offrom about 10 psi to about 100 psi greater than the liquid streampressure. Evidence of the aforementioned beneficial results isdemonstrated, e.g., in the Examples provided herein.

In certain embodiments, the gaseous stream is introduced into the liquidstream toward the surface utilized in measurement of a parameter of theindustrial water in the industrial water system. In certain embodiments,the gaseous stream is introduced into the liquid stream in a directionperpendicular from the flow of the liquid stream. In certainembodiments, the gaseous stream is introduced into the liquid stream atan angle ranging from about ±45 degrees from a direction perpendicularfrom the flow of the liquid stream. In certain embodiments, the gaseousstream is introduced into the liquid stream at a location upstream ofthe surface utilized in measurement of a parameter of the industrialwater. In certain embodiments, the gaseous stream is introduced in thedirection of flow of the liquid stream. In certain embodiments, thegaseous stream is introduced into the liquid stream such that the liquidstream flowing across the surface utilized in measurement of a parameterof the industrial water in the industrial water system is unimpeded by agaseous stream delivery vessel. For example, as illustrated in FIG. 1b ,gaseous stream 130 is delivered into liquid stream 120 without placingdelivery equipment, or equipment of any kind, into the flow of liquidstream 120.

The gaseous stream of the embodiments described herein may comprise anyone or more of several gaseous substances. The gaseous stream maycomprise gaseous substances ranging from alkaline to inert to acidic. Incertain embodiments, the gaseous stream comprises a gaseous substanceselected from the group consisting of air, nitrogen, oxygen, an acidgas, an alkaline gas (e.g., gaseous ammonia), and combinations thereof,with the caveat that the acid gas and the alkaline gas are not incombination.

The term “acid gas” refers to a gaseous substance that, if combined with(e.g., dissolved in) water, turns the water acidic. Exemplaryembodiments of acid gases include certain carbon-containing gases,sulfur-containing gases, nitrogen-containing gases, andchlorine-containing gases. An exemplary embodiment of acarbon-containing acid gas is carbon dioxide. An exemplary embodiment ofa sulfur-containing acid gas is sulfur dioxide. An exemplary embodimentof a nitrogen-containing acid gas is nitrogen dioxide. An exemplaryembodiment of a chlorine-containing acid gas is chlorine.

Acid gases that may be utilized to practice the inventive methodsinclude, but are not limited to, a carbon-containing acid gas, asulfur-containing acid gas, a nitrogen-containing acid gas, achlorine-containing acid gas, and combinations thereof. An embodiment ofa carbon-containing acid gas is carbon dioxide. An embodiment of asulfur-containing acid gas is sulfur dioxide. An embodiment of anitrogen-containing acid gas is nitrogen dioxide and precursors thereof.An embodiment of a chlorine-containing acid gas includes chlorine.

Not wishing to be bound by theory, it is believed that the introductionof a gaseous stream into the liquid stream transfers mechanical energyto the surface utilized for measuring a parameter, thereby tending tophysically (as opposed to chemically) remove or inhibit deposition.Should the gaseous stream tend to be acidic, the removal or inhibitionof deposition is believed to be accomplished via physical and chemicalaction associated with introduction of the acid gas, which is believedto hold true for an alkaline gaseous stream as well.

In certain embodiments, pellets of carbon dioxide are introduced withthe gaseous stream into the liquid stream, which may be an industrialwater stream. The phrase “pellets of carbon dioxide” refers to solidpellets comprising carbon dioxide and possibly other substances. Carbondioxide pellets of the present disclosure are available from AllteqIndustries, Inc., 355 Lindbergh Ave., Livermore, Calif., and KyodoInternational, Inc., 9-10-9 Miyazaki, Miyamae-ku, Kawasaki-shi,Kanagawa-ken, 216-0033, Japan. The pellets may be generally spherical.In certain embodiments, the pellets have a diameter of from about 0.1 μmto about 0.3 mm, including from about 0.1 μm, or about 1 μm, or fromabout 10 μm, to about 0.1 mm, or to about 0.2 mm, or to about 0.3 mm.

As shown in FIG. 1d , gaseous stream 130, which would include thepellets of carbon dioxide, can be fed pneumatically into the liquidstream through nozzles 3110 a and/or 3110 b, which replace countersinkedopenings 2110 a and/or 2110 b when implemented. The pellets may beintroduced into the gaseous stream along with any of the gaseoussubstances disclosed herein. Preferred gases to utilize in delivery ofthe carbon dioxide pellets include, e.g., at least one of air andgaseous carbon dioxide.

FIG. 1e illustrates an embodiment of a system that may be utilized toperform the introduction of the carbon dioxide pellets into gaseousstream(s) 130, e.g., via stream 185. A person of skill in the art willrecognize that stream 185 should be configured to provide effective feedof the carbon dioxide pellets such that the resulting combined gaseousstream 130 provides adequate contact to any or all of surfaces 1110.

Any surface critical to the measurement of one or more parameters ofindustrial water utilized in an industrial water system is contemplatedby the methods of the present disclosure. The phrase “industrial waterutilized in an industrial water system” is intended to includeindustrial water that is, has been, or will be used in an industrialwater system. As it is commonly used, the term “stream” denotes fluidflow, generally through a conduit (e.g., a pipe).

By way of example, sensors that may be utilized in measuring parametersof industrial water in an industrial water system include, but are notlimited to, a temperature sensor, a pH sensor, an oxidation-reductionpotential sensor, a corrosion detection sensor, an optical sensor, aweight-measuring sensor, and a flow meter. Multiple sensors may beutilized for monitoring and optionally controlling an industrial watersystem, which may include multiple sensors of a single type of sensor(e.g., two fluorometers), multiple types of sensors (e.g., a pH sensor,an oxidation-reduction potential sensor, and a fluorometer), andcombinations thereof (e.g., two fluorometers, a pH sensor, and threeoxidation-reduction potential sensors).

Reference to the term “optical sensor” is made to denote a device thatat least in part relies on light transmission and detection to determinea parameter associated with a substance. For example, a fluorometer maydetermine the concentration of a chemical species in a liquid bytransmitting light at an excitation wavelength into the liquid, anddetecting light at an emission wavelength out of the liquid. Dependingon the application and substance, optical sensors may measure, forexample, fluorescence, absorption, temperature, chemiluminescence,optical scattering (e.g., Rayleigh, Mie, and Raman scatter), imaging,transmittance, particle size, particle count, and turbidity.

At a minimum, an optical sensor is capable of receiving an opticalsignal to detect a parameter of a substance. The optical sensor may alsosend an optical signal that may be used to generate the optical signalreceived by the optical sensor. If an optical signal is generated, it istypically directed to a particular location. An optical signal may, forexample, be directed to shine through a light transference medium andinto a liquid (e.g., an industrial water stream) in order to perform anoptical measurement of a parameter of the liquid using the same or adifferent optical sensor. Reference to the term “optical measurement”denotes using light to determine a parameter of a substance using anoptical sensor.

By way of example, embodiments of an optical sensor include, but are notlimited to, a fluorometer, a spectrophotometer, a colorimeter, arefractometer, a luminometer, a turbidimeter, and a particle counter.Multiple optical sensors may be utilized for monitoring and optionallycontrolling an industrial water system, which may include multipleoptical sensors of a single type of optical sensor (e.g., more than onefluorometer), multiple types of sensors (e.g., a fluorometer and acolorimeter), and combinations thereof (e.g., two fluorometers, aspectrophotometer, and three refractometers). Generally, the surfacecritical to the measurement of one or more parameters using an opticalsensor is a wetted surface of a light transference medium.

By way of example, embodiments of surfaces critical to the measurementof one or more parameters of industrial water in an industrial watersystem include, but are not limited to, a wetted surface of atemperature sensor, a wetted surface of a pH sensor, a wetted surface ofan oxidation-reduction potential sensor, a wetted surface of a corrosiondetection sensor, a wetted surface of a light transference medium, awetted surface of a corrosion coupon, a wetted surface of a flow meter,and combinations thereof.

A light transference medium allows light to transfer through itself, or,if appropriate, reflect from itself, so that the light may be used toperform an optical measurement of a parameter of a substance using anoptical sensor. Preferably, light transference media are used foroptical transference, and hence are preferably transparent as defined inASTM D1746. However, depending on the particular application, completetransparency of a light transference medium may not be necessary.Examples of light transference media include a flow cell, an opticalwindow, a reflective surface, a refractive surface, a dispersiveelement, a filtering element, and an optical fiber sensor head.Prevention or removal of deposition on a wetted surface of a lighttransference medium should lead to greater transparency or, in someembodiments, light reflectance, of the light transference medium, whichshould lead to more accurate measurements via an optical sensor.

As suggested by the previous paragraph, in some embodiments, a lighttransference medium comprises a surface utilized to reflect light. Thelight may partially or totally reflect from the reflective surface ofthe light transference medium.

In certain embodiments utilizing a flow cell as a light transferencemedium, the method further comprises fanning the combined gaseous andindustrial water stream as it flows toward the wetted surface of thelight transference medium. While not wishing to be bound by theory, thefanning is performed so as to provide better inhibition and/or removalof deposition on the wetted surface of the flow cell by forcing the gasof the combined gaseous and industrial water stream to come in bettercontact with the wetted surface of the light transference medium.

FIG. 2 illustrates an embodiment of a system 200 for performing methodsof the present disclosure, wherein the system 200 incorporates a opticalsensor 205 coupled with a flow cell 210, an exemplary embodiment of alight transference medium, having a wetted surface 1210. As illustrated,a liquid stream 120 flows through flow cell 210. Upstream from flow cell210, gaseous stream 130 is introduced into liquid stream 120. Thecombined gaseous and liquid stream 150 flows so as to contact the wettedsurface 1210 of the flow cell 210.

The contacting may be enhanced via nozzle 180, which may be configuredso as to provide further turbulence through the flow cell 210. Nozzle180 may be constructed and positioned so as to provide varying degreesof fanning (α, β) toward the wetted surface 1210 of flow cell 210.

In certain embodiments, the gaseous stream is introduced intermittentlyinto the industrial water stream. The terms “intermittent” and“intermittently” are utilized herein to describe the practice ofperforming a method or step thereof, ceasing performance of the methodor step thereof, and later repeating performance of the method or stepthereof, without regard to the timing of the performance. In certainembodiments of the illustrative embodiments, the gaseous stream isintroduced intermittently at pre-determined time intervals.

In certain embodiments, the gaseous stream is introduced on an as-neededbasis as determined via, e.g., measurement data trends. For example, aconsistent increase or decrease in measurement of a variable over time,even if slight, may indicate the need to introduce the gaseous streaminto the industrial water stream. An example of a consistent increase ordecrease could be illustrated by, e.g., a consistent change (i.e.,change in one direction) of ±about 1% to about 10% of a value over aperiod of time of, e.g., about 1 hour, when the sample water is known tobe approximately the same composition (e.g., no spikes in contamination)and at conditions (temperature, pressure, etc.) that are approximatelyunchanging. A consistent change in a measured variable can indicateobstruction (e.g., fouling) across the surface. After performing amethod as described herein, post-cleaning measurements utilizing thesurface can be compared to determine whether obstruction of the surfaceis causing the variability, or whether the sensor performing themeasurements is failing, which is further described herein.

A method of operating a cooling water system is also provided. Themethod comprises contacting a cooling water stream at a cooling waterstream pressure with a surface utilized for measuring a parameter with asensor. A gaseous stream is introduced into the cooling water stream,thereby causing the combined gaseous and cooling water stream to contactthe surface. The gaseous stream introduced at a gaseous stream pressureof from about 10 psi to about 100 psi greater than the cooling waterstream pressure. Introduction of the gaseous stream causes the combinedgaseous and cooling water stream to contact the surface.

In certain embodiments, the surface utilized in measurement of aparameter of the industrial water system is located in a narrowedportion of the liquid stream.

As discussed herein, in certain embodiments, the liquid stream comprisesa cleaning solution. FIG. 3 shows an embodiment of a system thatincorporates aspects of the embodiments illustrated in FIGS. 1a, 1b ,and 2, and further comprises a system for administering a cleaningsolution into the wetted portions of the system. A person skilled in theart will recognize that the embodiments of FIGS. 1c and 1e , thoughomitted from FIG. 3, can be implemented into the embodiment of FIG. 3.Furthermore, the skilled artisan will recognize that FIG. 3 shows anembodiment of the isolated first subset of sensors as described in themethod that utilizes a plurality of parameters, further describedherein.

In the embodiment of FIG. 3, a cleaning solution is supplied to thewetted surfaces 1110 a, 1110 b, and 1210, of pH sensor 110 a,oxidation-reduction potential sensor 110 b, and flow cell 210, via acleaning solution supply tank 301 and a cleaning solution pump 302. Aperson skilled in the art will recognize that the cleaning solutionsupply tank 301 and the cleaning solution pump 302 are merelyillustrative embodiments of apparatuses that may be utilized to providea cleaning solution to the wetted surfaces 1110 a, 1110 b, and 1210.

In certain embodiments, the cleaning solution is an aqueous cleaningsolution. In some embodiments, the cleaning solution comprises water andan ingredient selected from the group consisting of: a urea salt, amineral acid, an organic acid, a peroxyacid, a detergent, an emulsifier,and combinations thereof. A person of ordinary skill in the art willrecognize that certain chemical species will fit the description of morethan one of the aforestated ingredients.

Exemplary urea salts include, but are not limited to, urea hydrogenchloride, urea hydrogen sulfate, urea hydrogen nitrate, and ureahydrogen phosphate. Exemplary mineral acids include, but are not limitedto, hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, andboric acid. Exemplary organic acids include, but are not limited to,carboxylic acid, acetic acid, peracetic acid, citric acid, and oxalicacid. In some embodiments, the cleaning solution comprises water and aningredient selected from the group consisting of: urea hydrogenchloride, phosphoric acid, sulfuric acid, nitric acid, a peroxyacid, adetergent, an emulsifier, and combinations thereof. In a preferredembodiment, the aqueous cleaning solution comprises water and ureahydrogen chloride.

In certain embodiments, the aqueous cleaning solution (i.e., a cleaningsolution comprising water) has a solids concentration of from about 1weight percent solids to about 99 weight percent solids, including fromabout 1 weight percent solids, or about 10 weight percent solids, orfrom about 20 weight percent solids, or from about 30 weight percentsolids, to about 40 weight percent solids, or to about 60 weight percentsolids, or to about 90 weight percent solids, or to about 99 weightpercent solids. The phrase “weight percent solids” is used to denote thepercent by weight of the aqueous cleaning solution that is made up ofone or more ingredients other than water. In a preferred embodiment, theaqueous cleaning solution comprises water and urea hydrogen chloride,wherein the urea hydrogen chloride is present in the aqueous cleaningsolution at a concentration of from about 10 weight percent to about 90weight percent, including from about 10 weight percent, or from about 20weight percent, or from about 30 weight percent, to about 60 weightpercent, or to about 80 weight percent, or to about 90 weight percent.

Exemplary embodiments of peroxyacids include, but are not limited to,peracetic acid, peroxtanoic acid, and combinations thereof.

Exemplary embodiments of detergents include, but are not limited to,diethylene glycol, polyoxyethylene stearate, tridodecylmethylammoniumchloride, sodium dodecylsulfate, dihexadecyl phosphate,octylphenylpolyethylene glycol (e.g., compositions of CAS No.9002-93-1), and combinations thereof.

An exemplary embodiment of an emulsifier includes, but is not limitedto, sodium xylene sulfonate.

In a particularly preferred embodiment, the method chemically cleans atleast one of a wetted surface of a pH sensor and a wetted surface of anoxidation-reduction potential sensor utilizing aqueous urea hydrogenchloride, and the responsiveness of the utilized pH sensor and/oroxidation-reduction potential sensor is monitored by comparinghistorical data gathered during previous chemical cleaning cycles.Generally, as pH and oxidation-reduction potential sensors age, adecomposition process occurs in their respective sensing components,thereby changing the chemical composition of membranes utilized in each.Average lifetime for a pH or oxidation-reduction potential sensor isapplication dependent and can range from a few weeks to greater than ayear. Assuming that the industrial water system is in operation for anextended period of time, the pH sensor and/or oxidation-reductionpotential sensor will need to be replaced.

The decomposition process results in the thickening of a hydrated gellayer, which makes up the sensing component of a pH sensor and anoxidation-reduction potential sensor. Thickening of the hydrated gellayer causes less dynamic change in the hydrated gel layer, which canlead to inaccurate measurement of the respective parameters. Damage ordegradation of the hydrated gel layer can occur due to numerous sources,such as, e.g., exposure to high acidic or alkaline chemistry, mechanicalcleaning, high temperature, deposition, etc. As a result, the responsetime for the probe becomes slower and calibration must be done morefrequently than for less utilized sensors.

Measuring response times of pH sensors and oxidation-reduction potentialsensors has generally been limited to data collection during calibrationprocedures that involve removing the sensors and placing them in a knownstandard solution. Using the chemical cleaning method of the presentdisclosure, response time can be compared against previously collecteddata to assess sensor degradation. In embodiments utilizing multiplesensors of the same type, a comparison against redundant sensors exposedto the same process stream and cleaning solution can also provideinformation related to the response times of each sensor. A slowresponse or measurement offset from one sensor compared against anotherwould be an indication of degradation.

In a preferred embodiment, the method utilizes chemical cleaning withaqueous urea hydrogen chloride and further comprises isolating a firstsubset of surfaces from an industrial water stream, wherein the firstsubset of surfaces comprises a wetted surface of a pH sensor and awetted surface of an oxidation-reduction potential sensor. The firstsubset of surfaces is cleaned by contacting it with an aqueous ureahydrogen chloride cleaning solution for a period of time sufficient toreturn the pH sensor and the oxidation-reduction potential sensor to anacceptable level, which can be determined based on, e.g., a previouscalibration and/or measurements taken following the re-establishment ofcontact of the liquid stream to the surface utilized in measurement. ThepH signal decreases and the oxidation-reduction potential signalincreases because urea hydrogen chloride is both an acid and anoxidizer.

The cleaning solution may contact the wetted surfaces of the isolatedsubset, which may include a light transference medium. In an embodiment,the chemical solution may flow through the isolated subset for about 3minutes at a rate of about 3 gallons per day. In certain embodiments,once filled, the cleaning solution contacts the wetted surfaces withoutflowing for a period of time. In other embodiments, the cleaningsolution is immediately flushed from the wetted surfaces upon acceptablecleaning, which may be done using industrial water from the industrialwater system.

When industrial water flow is re-initiated, the pH andoxidation-reduction potential signals return back to industrial waterconditions following a double exponential decay for oxidation-reductionpotential sensors, and growth for pH sensors. The characteristic timeparameters calculated from the double exponential analysis give insightinto the decomposition, or lack thereof, in the oxidation-reductionpotential sensor and/or pH sensor. Historically tracking selectedparameters over time, the oxidation-reduction potential sensor (and acorresponding pH sensor, if utilized) can be monitored or replaced asneeded. In certain embodiments of the illustrative embodiments, theoxidation-reduction potential sensor is replaced periodically, forexample, every 4-8 months. In certain embodiments of the illustrativeembodiments, the pH sensor is replaced periodically, for example, every4-8 months.

When used, a pH sensor may show signs of sporadic measurement variationor sluggish response time during calibration, either of which suggeststhat deposition may be occurring on the wetted surface of the pH sensor.Either phenomenon may cause the affected pH sensor to fail calibration.

Data showing the dynamic behavior of an oxidation-reduction potentialsensor after exposure to aqueous urea hydrogen chloride is shown inTable 1. Exemplary features of the oxidation-reduction potentialsensor's signal behavior are labeled in Table 1. Response time afterexposing the oxidation-reduction potential sensor to industrial water ofan industrial water system shows a characteristic two-phase model toaccount for the fast and slow response behavior given by Formula 1:ORP(t)=Ae ^(−τ) ^(f) ^(t) +Be ^(−τ) ^(s) ^(t)+Offset  (1)wherein A is constant for the fast response term, τ_(f) is the fast timeconstant, B constant for the slow response term, τ_(s), is the slow timeconstant, and the Offset is the approximate oxidation-reductionpotential sensor signal just prior to the sensor contacting the aqueousurea hydrogen chloride (an example of a cleaning solution). Afterexposing the oxidation-reduction potential sensor to aqueous ureahydrogen chloride, the sensor response increases due to oxidation causedby the aqueous urea hydrogen chloride. At time t=0 after the industrialwater stream begins to contact the cleaned surface, the sum of theconstants A, B and Offset equals the sensor signal level. The signallevel tends to decay following the sum of the terms in Formula 1,wherein the critical parameters associated with the sensor responsebehavior are the time constants τ_(f) and τ_(s). The reciprocal of thetime constants allows for the estimation of the decay time to reach theOffset. In particular, an increase in the value of 1/τ_(s) for a sensorindicates that the sensor's response is degrading.

In a further aspect, the method comprises contacting an industrial waterstream at an industrial water stream pressure with at least one of awetted surface of a pH sensor and a wetted surface of anoxidation-reduction potential sensor. The pH and/or oxidation-reductionpotential of the industrial water stream is measured. A cleaningsolution comprising urea hydrogen chloride is contacted with at leastone of the wetted surfaces for a first period of time and at aconcentration sufficient to clean the at least one of the wettedsurfaces. The industrial water stream is re-contacted with the cleanedat least one of the wetted surfaces at the industrial water streampressure for a second period of time, thereby measuring pH and/oroxidation-reduction potential of the industrial water stream usingcleaned pH and/or oxidation-reduction potential sensors. A recoverycurve is created that is related to the measured pH and/or the measuredoxidation-reduction potential using the cleaned pH and/oroxidation-reduction potential sensors. The aforementioned steps arerepeated. The respective recovery curves are compared (and ideally wouldoverlap each other). If the comparison of the respective recovery curvesdemonstrates acceptable sensor degradation, the respective sensor mayremain in service. However, if the respective sensor demonstratesunacceptable sensor degradation, the respective sensor is removed fromservice.

For example, FIG. 4 illustrates recovery curves related to two differentsensors and allows for the comparison of the oxidation-reductionpotential sensor response for an aged sensor probe (greater than 4months of service) and a new sensor probe exposed to the same water anda urea hydrogen chloride cleaning step. The cleaning step involvedexposure of the sensing surface of the sensor probe to urea hydrogenchloride for 3 minutes at a rate of 10 gallons per day and aconcentration of 60 weight percent solids, followed by 2 minutes ofindustrial water flow at 2 gallons per minute. FIG. 4 shoes thenormalized signal response from each sensor probe at the end of thecleaning process. From FIG. 4, the response time for the aged sensor islonger compared to the new one. Quantitative analysis of the sensorresponse time is obtained by fitting the data to Formula 1 to determinethe fast and slow time constants. The parameters for Formula 1 can becalculated and stored for historical tracking, which has been done inTable 1 below.

TABLE 1 Exemplary response time parameters for an oxidation- reductionpotential sensor that utilizes a two-phase model. Contact time Δ PeakFWHM 1/τ_(f) 1/τ_(s) A B Offset (min) (mV) (min) (min) (min) (mV) (mV)(mV) 0 145 13 10.1 10.1 113.7 20.7 402.4 47 75 16 8.3 180.5 68.8 60.2378.6 274 105 20 8.0 28.3 38.9 43.2 413.7 385 97 19 13.9 64.5 77.7 25.8412.6 1467 126 14 7.8 94.5 102.7 34.6 393.3 1721 126 17 10.0 88.9 102.334.9 396.5 1952 122 20 9.8 117.2 88.8 39.0 400.3

The mathematical relationship of Formula 1 can be applied to model theresponsivity of a pH sensor as well, according to Formula 2 shown below.1/pH(t)=Ae ^(−τ) ^(f) ^(t) +Be ^(−τ) ^(s) ^(t)+Offset  (2)As can be seen from Formula 2, the pH sensor signal follows a growthresponse since exposure to urea hydrogen chloride causes a decrease inpH, followed by an increase when exposed to industrial water flow. Atypical pH sensor response curve resulting from a urea hydrogen chloridecleaning process as described above is shown in FIG. 5. The timeconstants of a pH sensor probe are determined in the manner describedfor the oxidation-reduction potential sensor probe, except for takinginto account that the pH sensor response is the reciprocal.

In certain embodiments, unacceptable sensor degradation is determined bya deviation in measured pH and/or oxidation-reduction potential of atleast about 5% at an equivalent point in time subsequent there-contacting the sensor with the industrial water stream. In certainembodiments, unacceptable sensor degradation is determined by adeviation in measured pH and/or oxidation-reduction potential of atleast about 10% at an equivalent point in time subsequent there-contacting the sensor with the industrial water stream. In certainembodiments, the equivalent point in time subsequent the re-contactingof the industrial water stream is a point in time from about 1 minute toabout 120 minutes subsequent the re-contacting of the industrial waterstream. In certain embodiments, the equivalent point in time subsequentthe re-contacting of the industrial water stream is a point in time fromabout 10 minutes to about 60 minutes subsequent the re-contacting of theindustrial water stream. For example, in FIG. 4, a comparison ofmeasured oxidation-reduction potential at points in time 50 minutessubsequent re-contacting (e.g., the curves have been normalized) showsthat the “New [ORP] Probe” measures an oxidation-reduction potential ofapproximately 0.1, while the “Aged [ORP] Probe,” which has been inservice for approximately 4 months, measures an oxidation-reductionpotential of approximately 0.4, which is 400% higher than measured bythe “New [ORP] Probe.” Comparing the curves over the span of theexperiment, the “Aged [ORP] Probe” never fully recovers and no longerprovides accurate measurement of oxidation-reduction potential. While apoint-in-time comparison is easily implemented, any similar comparisonof the deviation of recovery curves of measured pH and/oroxidation-reduction potential between a single pH or oxidation-reductionpotential sensor, or comparisons between a plurality of sensors of anysingle type are contemplated by the inventive method.

In an embodiment, a method of maintaining accuracy in the measurement ofa parameter of industrial water utilized in an industrial water systemis provided. In certain embodiments, the method accelerates recoverytime of an oxidation-reduction potential sensor and/or a pH sensor. Toachieve this acceleration, the method comprises contacting an industrialwater stream at an industrial water stream pressure with at least one ofa wetted surface of a pH sensor and a wetted surface of anoxidation-reduction potential sensor. A cleaning solution is contactedwith at least one of the wetted surface of the pH sensor and the wettedsurface of the oxidation-reduction potential sensor. The industrialwater stream is re-contacted with at least one of the wetted surface ofthe pH sensor and the wetted surface of the oxidation-reductionpotential sensor at the industrial water stream pressure. A gaseousstream is introduced into the industrial water stream at a gaseousstream pressure of from about 10 psi to about 100 psi greater than theindustrial water stream pressure and after initiation of there-contacting.

For example, at least one of an oxidation-reduction potential sensor anda pH sensor is exposed to chemical cleaning with, e.g., urea hydrogenchloride as described herein, followed by resuming contact of the atleast one sensor probe (i.e., a surface utilized in measurement of aparameter) with an industrial water stream, and then introducing agaseous stream into the industrial water stream at a gaseous pressure offrom about 10 psi to about 100 psi greater than the industrial waterstream pressure. The gaseous stream may be introduced according to anyof the parameters described herein related to the introduction of agaseous stream into a liquid stream. FIG. 6 illustrates results relatedto the introduction of a gaseous stream post-chemical cleaning, whereinthe gaseous stream is air.

In a further illustrative embodiment, the disclosure is directed to amethod of maintaining accuracy in the measurement of a plurality ofparameters of industrial water in an industrial water system. The methodcomprises contacting an industrial water stream at an industrial waterstream pressure with a plurality of surfaces utilized for measuring aplurality of parameters with a plurality of sensors. A first subset ofthe surfaces is isolated from the industrial water stream while a secondsubset of the surfaces maintains contact with the industrial waterstream. At least one surface of the first subset is cleaned while thesecond subset maintains contact with the industrial water stream.Contact with the industrial water stream is restored with the firstsubset of surfaces. The first subset of surfaces comprises at least oneof a wetted surface of a light transference medium, a wetted surface ofa pH sensor, and a wetted surface of an oxidation-reduction potentialsensor. The second subset of surfaces comprises at least one of a wettedsurface of a corrosion detection sensor and a wetted surface of aconductivity sensor.

An industrial water system that requires more than one surface formeasuring parameters with more than one sensor is operated in a mannerso that one or more surfaces that may be particularly affected bydeposition can be separated from contact with the industrial waterstream and cleaned. The embodiment may be implemented to allow forcontinued monitoring and optional control based on a subset of measuredparameters of the industrial water, while another subset of parametersis not measured during in situ cleaning of its related surface(s).

In some embodiments, the term “isolating” refers to stopping the flow ofthe industrial water stream across the first subset of surfaces withoutdisconnecting the industrial water system to manually clean one or moresurfaces, except for, in some instances, the removal of a corrosioncoupon (i.e., “system isolation”). Preferably, any data that may begenerated while the first subset of sensors is isolated from theindustrial water stream is not acted upon by a controller, as any suchdata that would be acquired during the subset's isolation would notreflect a parameter of the industrial water stream. In certainembodiments, corrosion coupons are utilized to provide data in additionto that provided by the several sensors of the embodiments disclosedherein.

In other embodiments, the term “isolating” refers to ceasing themeaningful collection of data using a sensor or subset of sensors (i.e.,“control scheme isolation”). As opposed to system isolation, a sensormay be isolated if it generates data that is intentionally ignored orotherwise intentionally not acted upon by a controller. A sensorisolated in the exemplary manner may allow for the sensor to be cleanedvia, e.g., introduction of a combined gaseous and liquid stream to awetted surface thereof. The isolated sensor would not need to beisolated from the industrial water stream, but only from the controlscheme. The term “meaningful data” as used herein refers to data thatdescribes a parameter of a substance and may be input into and reliablyacted upon by a control scheme.

For example, FIG. 7 illustrates an embodiment of a system that interalia combines several of the apparatuses and systems of the presentdisclosure, and may be utilized to perform any of the embodimentsdescribed herein.

FIG. 7 illustrates an embodiment of a system 400 that may be used tomonitor an industrial water system, which may be a cooling water system,a heating water system, a papermaking system, a refining system, achemical processing system, a crude oil extraction system, a natural gasextraction system, and so forth. During normal monitoring of theindustrial water system using system 400, an industrial water stream 420(corresponds to liquid stream 120 in FIGS. 1b and 1d ) flows at anindustrial water stream pressure through system 400 via conduits andfittings, thereby contacting a plurality of surfaces utilized formeasuring a plurality of parameters of the industrial water in theindustrial water system. Exemplary embodiments of the plurality ofsurfaces include, but are not limited to, wetted surface 1110 a of pHsensor 110 a, wetted surface 1110 b of oxidation-reduction potentialsensor 110 b, wetted surface 1210 of light transference medium (e.g.,flow cell) 210, wetted surface 1503 of corrosion detection sensor 1403,a wetted surface of conductivity sensor 1407, and wetted surface 1110 xof fluorometer 110 x (alternate embodiment of a light transferencemedium, shown in FIG. 1c ). In the embodiment of FIG. 7, pH sensor 110 aand oxidation-reduction potential sensor 110 b are mounted to system 400via apparatus 100, illustrated in FIGS. 1a, 1b, and 1d , and the lighttransference medium (e.g., flow cell) 210 is in operable communicationwith a fluorometer 205. The pH sensor 110 a, the oxidation-reductionpotential sensor 110 b, the fluorometer 205, the corrosion detectionsensor 1403, and the conductivity sensor 1407 are in communication withcontroller 1444, which collects and acts upon input provided by theplurality of sensors via a control scheme.

In the embodiment illustrated in FIG. 7, a first subset of the surfaces,which comprises at least one of wetted surface 1110 a of pH sensor 110a, wetted surface 1110 b of oxidation-reduction potential sensor 110 b,wetted surface 1210 of light transference medium (e.g., flow cell) 210,and/or wetted surface 1110 x of fluorometer 110 x, is isolated from theindustrial water stream while a second subset, which comprises at leastone of wetted surface 1503 of corrosion detection sensor 1403 and awetted surface of conductivity sensor 1407, maintains contact with theindustrial water stream 420. In the embodiment, the isolation of thefirst subset may be a system isolation performed by actuating valve 1411into its closed positions, or by control scheme isolation as describedherein. At least one of the first subset of surfaces is cleaned whilethe second subset maintains contact with the industrial water stream420, followed by restoration of contact of the industrial water stream420 to the first subset of surfaces.

The cleaning of the first subset or a wetted surface thereof can beperformed via at least one of the gaseous stream method(s) and thechemical cleaning method(s) disclosed herein. Furthermore, the isolatingmay be performed via at least one of system isolation and control schemeisolation, and need not be isolated in the same manner during repeatedcleaning cycles. Even further, a gaseous stream may be combined with aliquid stream other than the industrial water stream (e.g., a cleaningsolution stream) in order to clean the first subset or wetted surfacethereof.

The following examples further illustrate the invention but, of course,should not be construed as in any way limiting its scope.

Example 1

This example demonstrates the effect of gaseous stream cleaning of anoxidation-reduction potential sensor. Two identical oxidation-reductionpotential sensors were installed in a cooling water system. The coolingwater system maintained a stream of cooling water having pH of from 6.5to 7.6, conductivity of from about 1500 to about 2000 μS/cm,oxidation-reduction potential of from about 275 to about 325 mV,temperature of from 19 to 25° C., linear liquid stream speed of fromabout 0.68 to about 1.13 meters per second, and cooling water pressureof about 1 bar (approximately 14.5 psi). The wetted surface of Sensor Awas untreated, while the wetted surface of Sensor B was treated asdescribed herein with a gaseous stream of compressed air having apressure of about 3 bar (approximately 43.5 psi), for 60 seconds perfour hours.

Referring to FIG. 8, for the duration of the experiment, Sensor A tendedto drift from its base measurement of approximately 325 mV, while SensorB maintained a reasonably steady base measurement. By the end of thetesting period, the output of Sensor A had decreased approximately 125mV.

Example 2

This example demonstrates the effect of chemical cleaning of anoxidation-reduction potential sensor used in an industrial water system,which in this example was a cooling water system. Two identicaloxidation-reduction potential sensors were installed in a pilot coolingwater system. Sensor C was installed via a tee, while Sensor D wasinstalled via a sensor block as illustrated in FIGS. 1a and 1b . Thepilot cooling water system maintained a stream of cooling water havingpH of from 8.6 to 8.9, conductivity of from about 3000 to about 8500μS/cm, oxidation-reduction potential of from about 250 to about 450 mV,temperature of from 34 to 44° C., linear liquid stream speed of fromabout 0.34 to about 1.03 meters per second, and cooling water pressureof about 0.4 bar (approximately 5.8 psi). The oxidation-reductionpotential of the cooling water stream was verified using a calibratedMyron ULTRAMETER II™ 6 PFC^(E) oxidation-reduction potential meter,available from MYRON L® Company, 2450 Impala Drive, Carlsbad, Calif.92010, USA.

As shown in FIG. 9, at the end of the 10-day test period, Sensor Dmaintained a 95% output of 265 mV on average, while Sensor C erroneouslymeasured an oxidation-reduction potential of approximately 200 mV.

Example 3

This example demonstrates the effect of chemical cleaning of a lighttransference medium used in an industrial water system, which in thisexample was a cooling water system. A wetted surface of a fluorometerflow cell used in cooling water system at a steel plant was chemicallytreated. Two treatment periods having differing treatment chemistrieswere attempted: one using an aqueous mineral acid-based cleanercomprising water, phosphoric acid, and nitric acid (e.g., TR5500 acidcleaner, comprising about 30 to about 60 weight percent phosphoric acid,about 10 to about 30 weight percent nitric acid, balance water and traceimpurities, available from Nalco, an Ecolab Company, 1601 West DiehlRoad, Naperville, Ill. 60563), and a second using an aqueous ureasalt-based cleaner, for this example, an aqueous urea hydrogen chloridecleaner (e.g., DC14 cleaner, comprising about 30 to about 60 weightpercent urea hydrogen chloride, balance water and trace impurities,available from Nalco, an Ecolab Company, 1601 West Diehl Road,Naperville, Ill. 60563). For each of the two trials, a liquid streampassed across the wetted surface of the flow cell, with the liquidstream having pH of from 7.3 to 9.0, conductivity of from about 580 toabout 1570 μS/cm, oxidation-reduction potential of from about 200 toabout 760 mV, temperature of from 15 to 30° C., linear liquid streamspeed of from about 0.6 to about 1.03 meters per second, and liquidstream pressure of about 1 bar (approximately 14.5 psi). The flow of theliquid stream, when present, was from 1 to 2 gallons per minute.

For three minutes per day, the liquid stream was stopped from passingacross the wetted surface of the flow cell, and the respective chemicaltreatment was pumped across the wetted surface of the flow cell at arate of 10 gallons per day (i.e., 26.3 mL/min). After the three minutes,chemical treatment was stopped and the liquid stream resumed across thewetted surface of the flow cell.

As shown in FIG. 10, cell fouling was maintained at less than about 30%for approximately 25 days in the challenging high-fouling system of thepresent example by an acid cleaner comprising phosphoric and nitricacids.

As shown in FIG. 11, cell fouling was maintained at less than about 15%for approximately 35 days in the challenging high-fouling system of thepresent example by a urea-based cleaner comprising urea hydrogenchloride.

All references, including publications, patent applications, andpatents, cited herein are hereby incorporated by reference to the sameextent as if each reference were individually and specifically indicatedto be incorporated by reference and were set forth in its entiretyherein.

The use of the terms “a” and “an” and “the” and “at least one” andsimilar referents in the context of describing the invention (especiallyin the context of the following claims) are to be construed to coverboth the singular and the plural, unless otherwise indicated herein orclearly contradicted by context. The use of the term “at least one”followed by a list of one or more items (for example, “at least one of Aand B”) is to be construed to mean one item selected from the listeditems (A or B) or any combination of two or more of the listed items (Aand B), unless otherwise indicated herein or clearly contradicted bycontext. The terms “comprising,” “having,” “including,” and “containing”are to be construed as open-ended terms (i.e., meaning “including, butnot limited to,”) unless otherwise noted. Individual embodiments, orelements thereof, may comprise, consist of, or consist essentially ofthe recited elements, unless the context clearly indicates otherwise. Inother words, any recitation of a statement such as “x comprises y”includes the recitations of “x consisting of y” and “x consistingessentially of y.” Recitation of ranges of values herein are merelyintended to serve as a shorthand method of referring individually toeach separate value falling within the range, unless otherwise indicatedherein, and each separate value is incorporated into the specificationas if it were individually recited herein. All methods described hereincan be performed in any suitable order unless otherwise indicated hereinor otherwise clearly contradicted by context. The use of any and allexamples, or exemplary language (e.g., “such as”) provided herein, isintended merely to better illuminate the invention and does not pose alimitation on the scope of the invention unless otherwise claimed. Nolanguage in the specification should be construed as indicating anynon-claimed element as essential to the practice of the invention.

Preferred embodiments of this invention are described herein, includingthe best mode known to the inventors for carrying out the invention.Variations of those preferred embodiments may become apparent to thoseof ordinary skill in the art upon reading the foregoing description. Theinventors expect skilled artisans to employ such variations asappropriate, and the inventors intend for the invention to be practicedotherwise than as specifically described herein. Accordingly, thisinvention includes all modifications and equivalents of the subjectmatter recited in the claims appended hereto as permitted by applicablelaw. Moreover, any combination of the above-described elements in allpossible variations thereof is encompassed by the invention unlessotherwise indicated herein or otherwise clearly contradicted by context.

The invention claimed is:
 1. A method comprising: contacting anindustrial water stream at an industrial water stream pressure with aplurality of surfaces utilized for measuring a plurality of parametersof an industrial water in an industrial water system; isolating a firstsubset of the surfaces from the industrial water stream while a secondsubset of the surfaces maintains contact with the industrial waterstream; cleaning at least one surface of the first subset of surfaceswhile the second subset of surfaces maintains contact with theindustrial water stream; and restoring contact of the industrial waterstream with the first subset of surfaces; wherein the first subset ofthe surfaces comprises at least one of a wetted surface of a pH sensor,a wetted surface of an oxidation-reduction potential sensor, and awetted surface of a light transference medium; and wherein the secondsubset of the surfaces comprises at least one of a wetted surface of acorrosion detection sensor and a wetted surface of a conductivitysensor.
 2. The method of claim 1, wherein the cleaning comprisescontacting a combined gaseous and liquid stream with the at least onesurface of the first subset.
 3. The method of claim 2, wherein thecombined gaseous and liquid stream comprises a cleaning solution.
 4. Themethod of claim 3, wherein the cleaning solution comprises aqueous ureahydrogen chloride.
 5. The method of claim 3, wherein the cleaningsolution comprises an ingredient selected from urea hydrogen chloride,phosphoric acid, sulfuric acid, nitric acid, a peroxyacid, a detergent,an emulsifier, or a combination thereof.
 6. The method of claim 2,wherein a gaseous stream having a gaseous stream pressure is introducedinto a liquid stream at a liquid stream pressure to form the combinedgaseous and liquid stream.
 7. The method of claim 6, wherein the gaseousstream pressure is from 10 to 100 psi greater than the liquid streampressure.
 8. The method of claim 6, wherein the gaseous stream isintroduced in a direction perpendicular from the liquid stream.
 9. Themethod of claim 6, wherein the gaseous stream comprises an acid gasselected from a carbon-containing acid gas, a sulfur-containing acidgas, a nitrogen-containing acid gas, a chlorine-containing acid gas, ora combination thereof.
 10. The method of claim 6, wherein pellets ofcarbon dioxide are introduced with the gaseous stream into the liquidstream.
 11. The method of claim 6, wherein the gaseous stream isintroduced intermittently into the liquid stream.
 12. The method ofclaim 2, wherein the combined gaseous and liquid stream comprises agaseous substance selected from air, nitrogen, oxygen, an acid gas, or acombination thereof.
 13. The method of claim 2, wherein the first subsetof surfaces comprises a wetted surface of a light transference medium.14. The method of claim 13, further comprising fanning the combinedgaseous and liquid stream as it flows toward the wetted surface of thelight transference medium.
 15. The method of claim 1, wherein thecleaning comprises contacting a cleaning solution with the at least onesurface of the first subset.
 16. The method of claim 15, wherein thecleaning solution comprises aqueous urea hydrogen chloride.
 17. Themethod of claim 15, wherein the cleaning solution comprises aningredient selected from urea hydrogen chloride, phosphoric acid,sulfuric acid, nitric acid, a peroxyacid, a detergent, an emulsifier, ora combination thereof.
 18. The method of claim 1, wherein the industrialwater system is selected from a cooling water system, a heating watersystem, a papermaking system, a refining system, a chemical processingsystem, a crude oil extraction system, and a natural gas extractionsystem.
 19. The method of claim 1, wherein the industrial water systemis a cooling water system.
 20. The method of claim 1, wherein at leastone of the surfaces is located in a narrowed portion of the industrialwater stream.